How is absolute pressure defined?

Absolute pressure is defined as the total pressure exerted by a fluid, taking into account the atmospheric pressure surrounding it. It is measured relative to a perfect vacuum, which means it includes the weight of the atmospheric pressure above the measurement point.

When referring to absolute pressure, one commonly encounters that it is equal to gauge pressure plus atmospheric pressure. Since standard atmospheric pressure at sea level averages about 14.7 psi, adding this value to gauge pressure—measured relative to atmospheric pressure—results in absolute pressure. This is why the definition that involves "pressure plus 14.7 psi" is an accurate reflection of absolute pressure.

This definition is crucial in various applications, including scientific research, engineering, and practical maintenance tasks, as it ensures that calculations and measurements account for the effects of the atmosphere.